Describe the bug

• Node.js version: v12.16.1
• OS & version: macOS 10.15.3

Actual behavior

Getting the following error message when making multiple requests with got:

(node:60669) MaxListenersExceededWarning: Possible EventEmitter memory leak detected. 11 error listeners added to [KeyvMemcache]. Use emitter.setMaxListeners() to increase limit

Expected behavior

For got/keyv to:

• not keep adding the event listener for each call, leading to the memory leak
• clean up the event listener (can add a teardown feature req in Keyv)

I expect this behavior especially when .extending:

const extendedGot = got.extend({ cache });

Code to reproduce

• I traced it back to keyv:L43
• The cache storage is passed into got, and got passes that into Keyv, which adds the event listener
• In the code below, I shim .on, but in practice I'm using keyv-memcache, which extends the EventEmitter which is what makes the warning about the memory leak

const got = require('got');

const cache = new Map();
cache.on = function(eventName) {
	console.trace(eventName);
};

// Individual calls
for (let i = 0; i < 10; i++) {
	got('http://google.com', { cache });
}

// Extended calls
const extendedGot = got.extend({ cache });
for (let i = 0; i < 10; i++) {
	extendedGot('http://google.com');
}

Checklist

• I have read the documentation.
• I have tried my code with the latest version of Node.js and Got.

For what it's worth, I also read #792, https://github.com/lukechilds/cacheable-request/issues/30, and #921 (the "click for solution" link is broken for me) but I believe the problem is different.